Light drives single-molecule nanoroadsters

November 04, 2016

Scientists at Rice University and at the University of Graz, Austria, are driving three-wheeled, single-molecule "nanoroadsters" with light and, for the first time, seeing how they move.

The Rice lab of nanocar inventor and chemist James Tour synthesized light-driven nanocars six years ago, but with the aid of experimental physicists in Austria, they're now able to drive fleets of single-molecule vehicles at once.

A report on the work appears in the American Chemical Society journal ACS Nano.

"It is exciting to see that motorized nanoroadsters can be propelled by their light-activated motors," said Tour, who introduced nanocars in 2005 and motorized them a year later. "These three-wheelers are the first example of light-powered nanovehicles being observed to propel across a surface by any method, let alone by scanning tunneling microscopy."

Rather than drive them chemically or with the tip of a tunneling microscope, as they will do with other vehicles in the upcoming international NanoCar Race in Toulouse, France, the researchers used light at specific wavelengths to move their nanoroadsters along a copper surface. The vehicles have rear-wheel molecular motors that rotate in one direction when light hits them. The rotation propels the vehicle much like a paddle wheel on water.

The team led by Tour and Leonhard Grill, a professor at the University of Graz and formerly at the Fritz-Haber-Institute, Berlin, used wavelength-sensitive modified motors invented by Dutch scientist Bernard Feringa, who shared this year's Nobel Prize in chemistry for his molecular machine.

Remote control is key to the cars' useful abilities. "If we have to 'wire' the car to a power source, like an electron beam, we would lose a lot of the cars' functionality," Tour said. "Powering them with light frees them to be driven wherever one can shine a light -- and eventually we hope they will carry cargo."

Another advantage is the ability to activate fleets of nanocars at once. "This is precisely what we seek -- to use a light to activate motors and have swarms of nanovehicles moving across the surface, made directional through electric field gradients," Tour said. "This would permit us the future prospect of using nanomachines like ants that work collectively to perform construction."

Grill said remote control by light eliminates the need for a local probe that would have to address the molecules one by one. "Additionally, no 'fuel' molecules are required that would contaminate the surface and modify the diffusion properties," he said.

Tour has used modified Feringa's motors to power his lab's nanosubmersibles. In this case, the motor is the back wheel. He said the three-wheeled configuration simplifies its use because larger nanocars are more difficult to put onto an imaging surface and often dissociated during deposition under vacuum, according to Grill.

Experiments by lead author Alex Saywell of the Grill group on nanoroadsters made at Rice demonstrated a need for a fine balance of light and temperature to allow "enhanced diffusion" of the molecules in a vacuum.

Grill said using light to drive nanomachines offers a fundamental advantage -- the ability to selectively induce motion because of the motors' sensitivity to wavelength. Ultraviolet light at 266 nanometers doubled the roadsters' movement compared with "control" roadster molecules without motors. At 355 nanometers, it tripled.

The roadsters, made of 112 atoms, reached a top speed of 23 nanometers per hour.

A surface activation temperature of 161 kelvins (minus 170 degrees Fahrenheit) proved best for driving conditions. If the temperature is too cold, the roadsters would stick to the surface; too warm and they would diffuse randomly without help from the motor.

"We were surprised by the very clear correlation of the enhanced motion to the presence of the motor, the need for both heat and light to activate this motion -- in perfect agreement with the concept of the Feringa motor -- and the wavelength sensitivity that nicely fit our expectations from spectroscopy in solution," Grill said.
-end-
Co-authors are Rice alumni Víctor García-López and Pinn-Tsong Chiang, and Anne Bakker, Johannes Mielke, Takashi Kumagai and Martin Wolf of the Max Planck Society, Berlin. Saywell is now the Marie Curie Research Fellow at University of Nottingham, United Kingdom. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice.

The National Science Foundation, the Marie Curie Intra-European Fellowship and the German Science Foundation supported the research.

Read the abstract at http://pubs.acs.org/doi/abs/10.1021/acsnano.6b05650

This news release can be found online at http://news.rice.edu/2016/11/04/light-drives-single-molecule-nanoroadsters/

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Tour Group at Rice: http://tournas.rice.edu/website/

Wiess School of Natural Sciences: http://natsci.rice.edu

Nanoscale Science Group (Grill): http://www.nanograz.com

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Rice University

Related Molecules Articles from Brightsurf:

Finally, a way to see molecules 'wobble'
Researchers at the University of Rochester and the Fresnel Institute in France have found a way to visualize those molecules in even greater detail, showing their position and orientation in 3D, and even how they wobble and oscillate.

Water molecules are gold for nanocatalysis
Nanocatalysts made of gold nanoparticles dispersed on metal oxides are very promising for the industrial, selective oxidation of compounds, including alcohols, into valuable chemicals.

Water molecules dance in three
An international team of scientists has been able to shed new light on the properties of water at the molecular level.

How molecules self-assemble into superstructures
Most technical functional units are built bit by bit according to a well-designed construction plan.

Breaking down stubborn molecules
Seawater is more than just saltwater. The ocean is a veritable soup of chemicals.

Shaping the rings of molecules
Canadian chemists discover a natural process to control the shape of 'macrocycles,' molecules of large rings of atoms, for use in pharmaceuticals and electronics.

The mysterious movement of water molecules
Water is all around us and essential for life. Nevertheless, research into its behaviour at the atomic level -- above all how it interacts with surfaces -- is thin on the ground.

Spectroscopy: A fine sense for molecules
Scientists at the Laboratory for Attosecond Physics have developed a unique laser technology for the analysis of the molecular composition of biological samples.

Looking at the good vibes of molecules
Label-free dynamic detection of biomolecules is a major challenge in live-cell microscopy.

Colliding molecules and antiparticles
A study by Marcos Barp and Felipe Arretche from Brazil published in EPJ D shows a model of the interaction between positrons and simple molecules that is in good agreement with experimental results.

Read More: Molecules News and Molecules Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.